The invention relates to a tubular shaft instrument.
In modern medicine, attempts are generally made to keep the damage to intact tissue to a minimum. Thus, when circumstances permit, minimally invasive surgery is usually the preferred method used to perform an operative intervention. Small incisions and little trauma to the tissue lead to a lower sensation of pain after the operation and to rapid recovery and mobilization of the patient. This also applies to laparoscopic surgery during which complex operations are performed in the abdominal cavity.
Operations of this type and the instruments required for them present a particular challenge to the manufacturers of medical instruments as the majority of the operative steps are performed in very restricted spaces and without direct visual contact. Thus the medical instruments used must not only be able to operate in the smallest spaces but must also function so reliably that visual monitoring is superfluous. The instruments are preferably constructed such that even without visual contact the operating surgeon always has feedback which enables him to draw conclusions about the progress of the operation.
This applies particularly to all instruments that are suitable for the separation of tissue. As scalpels having an open blade are, if anything, unsuitable for minimally invasive surgery (cf. DE 44 44 166 A1), scissors-type or tong-type instruments are frequently resorted to, which cover the blade during insertion of the instrument on one hand and simultaneously take on a holding function for the tissue to be cut on the other.
It has also proven advantageous in minimally invasive surgery to perform coagulation of the tissue prior to separation in order to prevent bleeding. It is known from prior art to provide instruments that have integrated coagulation and cutting devices. Here the tissue on a fixing plane is clamped and coagulated in a first step. In a second step, a knife having a blade, which is substantially perpendicular to the fixing plane and protrudes over the tissue on both sides, is guided through the tissue. This displacement is carried out substantially parallel to the fixing plane. This prior art emerges, for example, from U.S. 2003/0199870 A1, U.S. Pat. No. 6,679,882 B1, EP 717 960 B1, U.S. 2002/0188294 A1, WO 2005/004735 A1.
On the other hand, it is known from U.S. Pat. No. 6,626,901 B1 to roll a blade similar to a pizza cutter over the tissue, instead of the knife, and thus to perform the incision. Whilst the last-mentioned method is very intricate and makes particular demands on the design of the instrument, the other methods also have numerous drawbacks. In the last-mentioned method, the clamped tissue is essentially pushed out of the mouth part by the displacement of the knife and only part of the tissue held is separated. During separation, a high single-point load is exerted on the tissue which in turn means that there is no guarantee of a clean cut when the blade is worn. The tissue is crushed until it virtually tears. There is a danger that the cut edge will spread so far that it passes the coagulated region and the vessel seal already performed will tear open again. As the blade or cutter only rests on one point on the tissue, the cutter wears quickly.
The same reference numerals are used in the following description for identical parts and parts acting in an identical manner.